RNA interference (RNAi) is a near-ubiquitous post-transcriptional gene regulatory mechanism that is mediated by microRNAs (miRNAs). Gene knockdown by these small, non-coding RNAs exploits the RNA Induced Silencing Complex (RISC) which utilizes the seed region (positions 2-7) of the miRNA guide strand to target the 3'UTR of mRNA for transcript cleavage and/or translational attenuation. Since the discovery that short, synthetic dsRNAs (referred to as small interfering RNAs, siRNAs) can enter the pathway, RNAi has been adopted as a tool for functional genomics.